Annular fluids and method of emplacing the same

a technology of annular fluids and fluids, applied in the direction of sealing/packing, wellbore/well accessories, insulation, etc., can solve the problems of gas hydrate crystal formation, blockage of well pipes, and great obstacles to removal, and achieve the effect of substantially increasing the viscosity of the packer fluid

Inactive Publication Date: 2004-07-15
MI
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The present invention relates to a packer fluid that has low thermal conductivity and is suitable for use in oil and gas wells. The fluid includes a water-miscible solvent, a viscosifying additive, a crosslinking agent, and an initiating agent. The fluid has the ability to increase its viscosity when it is resident in the annulus of a well. The low thermal conductivity of the fluid helps to prevent heat loss and improve energy efficiency in the well. The invention also provides a method for preparing the packer fluid and a method for emplacing and removing the fluid. The technical effects of the invention include improved energy efficiency, reduced heat loss, and improved safety in oil and gas wells.

Problems solved by technology

Permafrost is a thick layer of frozen surface ground which may be several hundred feet thick and presents a great obstacle to the removal of relatively warm fluids through a well pipe.
Particularly, warm fluid in the well pipe causes thawing of the permafrost in the vicinity of the well resulting in subsidence which can impose compressive and / or tension loads high enough to rupture or collapse the well casing and hence allow the escape of well fluids.
Further, gas hydrate crystals may form, which can freeze together and block the well pipe.
In this process, damage to the well casing may occur when heat is transferred through the annulus between the well tubing and the casing.
The resulting thermal expansion of the casing can break the bond between the casing and the surrounding cement, causing leakage.
es. The agglomeration of these oil constituents can cause blocking or restriction of the wellbore, resulting in significant reduction or even catastrophic failure of the production operat
Although many of the above-described packer fluids function adequately, they fail to meet industrial and governmental concerns for the environment.
Particularly, many of the constituents of the above-described packer fluids are unacceptable from an environmental standpoint and are often prohibited for use by government regulation.
For example, the mineral oils and heavy crude oils required by several of the above-discussed patents are not permitted for use in areas such as the Gulf of Mexico.

Method used

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Examples

Experimental program
Comparison scheme
Effect test

example 2

[0028] Because the embodiment of Example 1 has desirable properties for use as an annular fluid, the process of initiating polymer crosslinking by addition of MgO is investigated in more detail. In the second example, a fluid having a density of 9.86 ppg and a .lambda. of about 0.14 btu / (hr.multidot.ft.multidot..degree. F.) was formulated similarly to Example 1, except that the magnesium oxide was not added as a slurry in ethylene glycol but as a dry powder. The magnesium oxide was found to be able to disperse thoroughly throughout the mixture without causing any locally high pH pocket that might lead to premature crosslinking. As in Example 1, the crosslinking occurred over the course of several hours, leading to an increase in the viscosity.

example 3

[0029] Next, the fineness of the MgO powder is investigated. In the third embodiment, a fluid having a density of 9.86 ppg and a .lambda. of about 0.14 btu / (hr.multidot.ft.multidot..degree. F.) was formulated similarly to Example 1, except that the magnesium oxide was a very fine powder in a highly reactive form, i.e., having small particle size, high surface area, and ready accessibility for reaction. One example of such a fine powder MgO is available commercially from M-I L.L.C under the trade name of Di-Balance.TM.. The fine powder MgO was added as a slurry in ethylene glycol. The magnesium oxide was found to be able to disperse thoroughly throughout the mixture without causing any locally high pH pocket that might lead to premature crosslinking. As in Example 1, the crosslinking occurred over the course of several hours, leading to an increase in the viscosity.

[0030] The above examples show that crosslinking may be initiated with the addition of MgO in various forms.

example 4

[0031] In the above examples, the divalent cation (Ca.sup.2+) is prevented from crosslinking DDHEC by the addition of acid (HCl). Subsequent addition of MgO counters the effect of HCl and allows the crosslinking to take place. Surprisingly, the order of the addition of the divalent cation and the acid has a dramatic effect on the ability of the resultant fluid to viscosify, as evidenced by the following example. In this example, a fluid having a density of 9.86 ppg and a .lambda. of about 0.14 btu / (hr.multidot.ft.multidot..degree. F.) was formulated from the same components as in Example 1, but in the following order:

2 1. Ethylene glycol 322.87 gm 2. ECF 680 16.8 gm 3. CaCl.sub.2 (dry) 70.0 gm 4. Concentrated HCl 2.38 gm 5. MgO 2.0 gm

[0032] The components were added in the order listed in the table. The first two components (ethylene glycol and ECF 680) were mixed and stirred together for about 1 hour to thoroughly disperse the polymer into the ethylene glycol. Then the dry calcium ...

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Abstract

An annular fluid or packer fluid, and methods of making the same, that includes a water-miscible solvent, a viscosifying additive, a crosslinking agent, a crosslinking inhibitor having the facility to inhibit crosslinking between the viscosifying additive and the crosslinking agent, and an initiating agent having the facility to overcome an action of the crosslinking inhibitor and to initiate crosslinking between the viscosifying additive and the crosslinking agent, is shown and described. The fluid has a thermal conductivity of no more than about 0.25 btu / (hr.ft.° F.) and a potential to substantially increase its viscosity upon sitting for a selected period of time.

Description

BACKGROUND OF INVENTION[0001] 1. Field of the Invention[0002] The invention relates generally to viscosifiable, low thermal conductivity annular fluids and methods of viscosifying, emplacing, and removing the fluids.[0003] 2. Background Art[0004] Annular fluids or packer fluids are liquids which are pumped into an annular opening between a casing and a wellbore wall or between adjacent, concentric strings of pipe extending into a wellbore. These fluids are especially necessary in oil or gas well construction operations conducted in low temperature venues of the world, for example, those areas having permafrost. Permafrost is a thick layer of frozen surface ground which may be several hundred feet thick and presents a great obstacle to the removal of relatively warm fluids through a well pipe. Particularly, warm fluid in the well pipe causes thawing of the permafrost in the vicinity of the well resulting in subsidence which can impose compressive and / or tension loads high enough to r...

Claims

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Application Information

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Patent Type & AuthorityApplications(United States)
IPC IPC(8): C09K8/12C09K8/512
CPCC09K8/512C09K8/12E21B33/12E21B33/138E21B36/00
InventorJONES, ANDREW G.K.PRASEK, BETHICIA B.HORTON, ROBERT L.
OwnerMI